RTS pin on AD5700

I am using AD5700 for HART 2 wire transmitter. In the design, AD5700 is interfaced with microcontroller ATxmega 128A4U. While starting the HART communication with HART master , I am facing the issue with RTS line. While transmission , my RTS pin does not go low to trasmit data from controller to modem AD5700. When i pull down the RTS line through a 1Mohm resistor, RTS pin goes low while transmission but that also happens sometimes. Sometimes it does not go low. Is there any specific software code needs to be written for the RTS pin. Right now i am using normal GPIO pin for RTS and configuring it as output pin.

This may have something to do with the configuration of your GPIO. You might not be setting the GPIO correctly when you try to communicate with AD5700. You were able to communicate with the AD5700 initially as the 10Mohm resistor or the termination of the oscilloscope probe pulls down the RTS pin. I suggest you should contact support from Atmel on how to configure the GPIO pins of your controller.

The RTS pin is an input pin so which needs to be pulled low by the controller to transmit data. There is no initialization needed on the RTS pin and the AD5700 only reacts depending on the input from the controller.

Can you send out your schematic detailing the connections made to the AD5700? Can you also send a scope shot of the signal lines to/from your controller to the AD5700? These information would help us understand more of your issue and understand what is causing the issue.

Can you also check your logic levels? These logic levels are very much dependent on the supply connected to the IOVCC pin of the AD5700.

Please find above schematic that i am using. I have shown the controller and AD5700 interfaces.

On AD5700 to controller lines, I am catching the RX, TX, CD and RTS lines. All are coming properly but RTS line is not going low while transmission from controller to AD5700.When I am putting 10M ohm resistance or even oscilloscope probe on RTS pin, it goes down and HART communication starts.

This may have something to do with the configuration of your GPIO. You might not be setting the GPIO correctly when you try to communicate with AD5700. You were able to communicate with the AD5700 initially as the 10Mohm resistor or the termination of the oscilloscope probe pulls down the RTS pin. I suggest you should contact support from Atmel on how to configure the GPIO pins of your controller.